Polypyrrole–Dopamine Nanofiber Light-Trapping Coating for Efficient Solar Vapor Generation

Abstract

Solar vapor generation (SVG) typically uses a solar absorbing material at the water–air interface to convert solar energy into heat for evaporation. However, the intrinsic solar absorption of the material determines the upper limit of the solar energy capture. By designing a light-trapping surface structure with open pores and channels, we can break this limit and further improve the absorption by enabling multiple reflections within the surface. Polypyrrole (PPy) is emerging as a promising solar thermal material. In this work, we propose an ultrasonic spray coating method to obtain a nanofiber light-trapping coating by copolymerization with dopamine (DA), which can be directly synthesized at room temperature rapidly (30 min). Due to its excellent wettability, this coating can transport water and can be directly coated on the thermal insulating layer, not requiring an additional water transport layer. This nanoscale coating significantly improves solar absorption at different incident angles across the full solar spectrum, achieving the highest solar-to-thermal conversion efficiency of 95.8% at 1.385 kg·m–2·h–1 under 1 sun. When applied on salt water, this solar evaporator achieves self-cleaning in the absence of solar irradiation. Moreover, the surface structure can be further tuned into granular/plane–fibrous/plane–granular structures by using different oxidants or surfactants, and their formation mechanisms are also proposed. This PPy–DA nanofiber coating shows great potential for SVG and other applications based on a PPy material, especially for those requiring a certain surface morphology.

Integrated Multi-Layered Fabric with Tunable Water Supply to the Photothermal Conversion Layer for an Efficient Solar Water Evaporation

“…43 This rough surface helps to reduce the reflection of light from the yarn surface and the scattering inside the yarn and enhances the ability of the yarn to absorb sunlight efficiently, which is further confirmed by UV−vis−NIR analysis. 44,45 In addition to the inherent elements C and O in cellulose fiber, the F element on the surface of polyester fiber (Figure 4c) shows that the hydrophobic finishing agent has been successfully coated on the surface of polyester fiber. As shown in Figure 4f, in the EDS spectrum of PPy/viscose yarn, the N element is evenly deposited on the surface of the viscose fiber and the N element is mainly produced by PPy particles.…”

Double-Sided Suspending Evaporator with Top Water Supply for Concurrent Solar Evaporation and Salt Harvesting

“…The suspending evaporator (3 cm in diameter) works steadily with DI water at the top water supply rate of 0.0165 mL/min, corresponding to 1.40 kg·m –2 ·h –1 , and the corresponding energy conversion efficiency is 95.7% (Figure a). The surface average temperature is 28.2 °C, which is much lower than that of a typical interfacial evaporator (40.3 °C) under the same test environment in our previous work . For this suspending evaporator, a lower surface average temperature indicates higher energy conversion efficiency.…”

“…The surface average temperature is 28.2 °C, which is much lower than that of a typical interfacial evaporator (40.3 °C) under the same test environment in our previous work. 44 For this suspending evaporator, a lower surface average temperature indicates higher energy conversion efficiency. The energy loss for the suspending evaporator only comes from the heat loss to the environment, mainly due to natural convection and thermal radiation.…”

Simple Design of a Porous Solar Evaporator for Salt-Free Desalination and Rapid Evaporation

“…Polypyrrole (PPy) is a well-known black conjugated conducting polymer with a broad absorption spectrum for light, making it an excellent solar photothermal material. , PPy has excellent chemical and thermal stability and is insoluble in water and other conventional solvents . Ma et al proposed a novel and facile ultrasonic spray method to prepare PPy-dopamine (DA) nanofiber light-harvesting coatings . The surface structure can be further tuned by using different oxidants and surfactants to obtain planar-fibrous or planar-granular composite structures.…”

“…17 Ma et al proposed a novel and facile ultrasonic spray method to prepare PPy-dopamine (DA) nanofiber light-harvesting coatings. 18 The surface structure can be further tuned by using different oxidants and surfactants to obtain planar-fibrous or planargranular composite structures. The highest solar heat conversion efficiency can reach 95.8%, and the evaporation rate is 1.385 kg m −2 h −1 .…”